Web analytics has evolved through three stages:
1) Server-side measurement of page requests (1995-2002)
2) Client-side tagging of pages (2002-present)
3) Hybrid client-server measurement and tag management (2008-present)
Measuring web traffic has transitioned from analyzing server log files to using page tags and tag management systems. Identifying unique users remains a challenge due to factors like cookie deletion and device sharing. Analytics aims to understand user behavior through metrics like pageviews, sessions, and conversion rates across various dimensions like time and content. Optimization testing helps continuously improve performance.